What does that even mean?

If you try to keep milk cold by putting it in the oven, that’s improper usage. It won’t stay cold.

If you’re saying people are trying to get high and are successful getting high, then it sounds like they’re accomplishing their goal and their usage of the product is proper for their intended use case.

Edit: Oh, you’re saying you don’t like what others are doing, but aren’t actually willing to state the fact that its just like your opinion man.

No, fears that leaving it available OTC would result in lots of people using it to make meth. Which, as far as I can tell, was a fantasy: yes, lots of people were using meth, but there was no real evidence that they were using OTC pseudoephedrine to do it. (And, as others have pointed out elsewhere in this discussion, there is no need to go through all the work of making it from pseudoephedrine when the Mexican drug cartels can provide it cheaper anyway.) Which makes the government's position rather like the old joke about the man who claimed to have invented anti-tiger dust:

Look at this wonderful anti-tiger dust I've invented?

But this is the USA, there are no wild tigers within thousands of miles of here.

See how effective my dust is?